We had an assembly error during the construction of our Deep Space robot that has left a very small portion of wedgetop tread that extends just slightly (less than 1/8") past the rear frame of our robot. This was due to 1) the wedgetop is actually thicker than the model stated and 2) a dimension was misread by one of our students.
The part that goes past the frame is the really “soft part” that would be compressed back easily by our bumpers. If this were an easy fix, I would not be asking this question. This fix alone will eat up an hour of our 6 hour robot access period so I have to ask the LRIs out there what my options are. Personally, this is so minor PLUS it gets pushed back in the frame by the bumpers that I think it should be okay. However, we cannot afford to show up and have an LRI flag this as a no go.
I would recommend sanding down/removing some tread at a small area of the wheel. If that part of the wheel can start the match facing to the outside of your robot then your problems might be solved!
You could also try thinner tread if sanding it down/removing some tread isn’t a workable solution.
I would not call that a minor protrusion, but if you want a final answer, I suggest you ask on the Q&A. And if I were you, I would be concerned about the increased friction between the tread and the bumper - that’ll impact your performance on the field and wear down your tread pretty quickly.
How close are you to the 120" frame perimeter? If you have an inch to spare then you could pre fab an extension plate that can rivet on the back of your frame to give you the right amount of extension.
That’s not a bad idea… We are very close but the actual measurements are 29-7/8 x 30. I do have a "bit to work with. Let me see how that works. I also just realized that we have one part that is not finished and I MIGHT be able of offset the wheel brackets by a smidge and make it work that way (maybe even in combo with this idea)
It may help people here help you better if you posted some photos of the part that protrudes and some photos showing the general arrangement of your robot.
In the future, don’t use the size/weight/extension limits as a design goal. Use a target that will guarantee you some margin so you can have an easy fix for issues like this.
The other reason I would highly recommend fixing this issue is from my experience, parts that move inside a robot rarely stay at there intended position for a lot of matches. Parts shift, bend, etc. While you might pass inspection (though I agree with most people in the thread that this wouldn’t pass inspection), if the part bends and moves farther outside of your frame perimeter, you could be looking at field violations that gets your robot disabled for a match if you can’t get inside a proper starting configuration.
Try switching to a Colson wheel that fits inside the frame. Sounds like you are using a 4" aluminum wheel with tread. Vex has a 3.5" and 3" Colson that might fit and not limit your climbing performance.
per Vex “Recommended use on robots up to 120lbs” This jack wheel is for a level 3 triple climbing system. Due to weight imbalances and the total max weight of the three robots, this is not suitable. When selecting this part, I was looking at a total load rating of 200 lbs per wheel min. The only part that fit that bill was the aluminum ones. However, if we cannot get our weight down, this might all be moot!
I now think I can fix this with the one set of unmounted wheels. Knowing this issue exists early enough has really helped…not to mention everyone’s great suggestions!
The trick was modifying the 3D CAD model with as built dimensions. If it were not for this, we would have found out during our 6 hour unbag time which would have been bad!
If you aim for an inch undersize on every side of the robot (ie. 116" frame perimeter), then the “growth” of the robot as you finish designing and building it won’t get you in trouble like this.
Yes, I speak from experience…that sizing box in 2008 was a bear!
Hopefully adding that plate will fix your problem. It’s a great suggestion.
It’s interesting in that R1 under Section 10.2 says…
Minor protrusions no greater than ¼ in. (~6 mm) such as bolt heads, fastener ends, weld beads, and rivets are not considered part of the FRAME PERIMETER.
But then the Starting Configuration ruleR right under it R2 says… which is more broad
In the STARTING CONFIGURATION (the physical configuration in which a ROBOT starts a MATCH), no part of the ROBOT shall extend outside the vertical projection of the FRAME PERIMETER, with the exception of its BUMPERS and minor protrusions such as bolt heads, fastener ends, rivets, cable ties, etc. If a ROBOT is designed as intended and each side is pushed up against a vertical wall (in STARTING CONFIGURATION and with BUMPERS removed), only the FRAME PERIMETER (or minor protrusions) will be in contact with the wall. The allowance for minor protrusions in R2 is intended to allow protrusions that are both minor in extension from the FRAME PERIMETER and cross sectional area.
I’ll second this idea. We had a feed wheel on our Stronghold robot that passed three inspections, but on the 4th proved to be 1/4" outside frame perimeter. We had to remount it in the pits and the ball feeder never worked properly again. Save yourself trouble and do it during unbag time when you can test and correct it as necessary.